Systems and methods for positioning a catheter

ABSTRACT

A method for displaying a position of a medical device, such as a catheter, during insertion of the medical device into a patient is disclosed. In one example embodiment, the method includes obtaining a first set of detected position data relating to a location marker, then determining a possible first position of the location marker. A first confidence level relating to a match between the first set of detected position data and a first set of predicted position data is assigned. A determination is made whether the first confidence level meets or exceeds a first threshold. If the first confidence level meets or exceeds the first threshold, a determination is then made whether the first position of the location marker is within a first detection zone. If the first position of the location marker is within the first detection zone, the first position of the location marker is displayed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 61/027,710, filed Feb. 11, 2008, and entitled “Systemsand Methods for Positioning a Catheter,” which is incorporated herein byreference in its entirety.

BRIEF SUMMARY

Briefly summarized, embodiments of the present invention are directed toa method for displaying a position of a medical device, such as acatheter, during insertion thereof into a patient.

In one example embodiment, the method includes obtaining a first set ofdetected position data relating to a location marker, then determining apossible first position of the location marker. A first confidence levelrelating to a match between the first set of detected position data anda first set of predicted position data is assigned. A determination ismade whether the first confidence level meets or exceeds a firstthreshold. If the first confidence level meets or exceeds the firstthreshold, a determination is then made whether the first position ofthe location marker is within a first detection zone. If the firstposition of the location marker is within the first detection zone, thefirst position of the location marker is displayed.

These and other features of embodiments of the present invention willbecome more fully apparent from the following description and appendedclaims, or may be learned by the practice of embodiments of theinvention as set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

A more particular description of the present disclosure will be renderedby reference to specific embodiments thereof that are illustrated in theappended drawings. It is appreciated that these drawings depict onlytypical embodiments of the invention and are therefore not to beconsidered limiting of its scope. Example embodiments of the inventionwill be described and explained with additional specificity and detailthrough the use of the accompanying drawings in which:

FIG. 1 illustrates an embodiment of a catheter being advanced throughthe vasculature of a patient to a destination;

FIG. 2A illustrates an embodiment of a stylet including a magneticlocation marker;

FIG. 2B illustrates an embodiment of a guidewire including a magneticlocation marker;

FIG. 2C illustrates an embodiment of a stylet including anelectromagnetic field-producing location marker;

FIG. 3 illustrates an embodiment of a tip location detector positionedproximate to the chest of a patient;

FIG. 4 illustrates the detector of FIG. 3 with a portion of anembodiment of a first detection zone and a portion of an embodiment of asecond detection zone superimposed thereon;

FIG. 5 illustrates another embodiment of a detector with a portion of anembodiment of a first detection zone and a portion of an embodiment of asecond detection zone superimposed thereon;

FIG. 6 illustrates an embodiment of a catheter tip within the firstdetection zone of the detector of FIG. 3;

FIG. 7 illustrates an embodiment of a display depicting the detector ofFIG. 3;

FIG. 8 illustrates the display of FIG. 6 showing an embodiment of amarker symbol representing a location of a catheter tip relative to thedetector of FIG. 3;

FIG. 9 illustrates an embodiment of a system configured to locate amarker and display a graphical representation of the marker;

FIG. 10 illustrates in simplified block format a tip location systemthat serves as one example environment in which embodiments of thepresent invention can be practiced;

FIG. 11 depicts various stages of a method for displaying a locationmarker associated with a medical device, according to one embodiment;and

FIG. 12 depicts various stages of a method for displaying the locationmarker associated with the medical device, according to one embodiment.

DETAILED DESCRIPTION OF SELECTED EMBODIMENTS

Reference will now be made to figures wherein like structures will beprovided with like reference designations. It is understood that thedrawings are diagrammatic and schematic representations of exemplaryembodiments of the present invention, and are neither limiting nornecessarily drawn to scale.

FIGS. 1-12 depict various features of embodiments of the presentinvention, which is generally directed to methods and systems fordetecting a location of a catheter, or of a catheter placement device,within a patient. Certain of such methods and systems relate moreparticularly to the detection and graphical representation of a locationof a catheter or catheter placement device. In some embodiments, thesystems and methods can represent the location relatively accuratelyand/or can reduce the number of erroneous identifications of thelocation, as further described below.

With reference to FIG. 1, in certain embodiments, a catheter 10 can beinserted in a vasculature 20 of a patient 25. The catheter 10 can beadvanced in a distal direction from an entry point 28 to a destination30, such as a target site or a desired or predetermined location withinthe patient 25. The catheter 10 can thus be advanced along a path 35through the patient. In some embodiments, the catheter 10 can comprise aperipherally inserted central catheter (“PICC”), a central venouscatheter (“CVC”), or another suitable catheter or medical device. Insome embodiments, the destination 30 for a distal end 50 of the catheter10 is within the superior vena cava (“SVC”). In other embodiments, thecatheter 10 can be advanced to other suitable destinations 30 within thepatient 25.

For clarity it is to be understood that the word “proximal” refers to adirection relatively closer to a clinician using the device to bedescribed herein, while the word “distal” refers to a directionrelatively further from the clinician. For example, the end of acatheter placed within the body of a patient is considered a distal endof the catheter, while the catheter end remaining outside the body is aproximal end of the catheter. Further, the words “including,” “has,” and“having,” as used herein, including the claims, shall have the samemeaning as the word “comprising.”

In certain embodiments, the catheter 10 is operably associated with alocation marker 40. The location marker 40 can be at the distal end 50of the catheter 10, and in some embodiments, may be integrally formedtherewith. The location marker 40 can comprise an energy emitter orfield producer of any suitable variety, and can include one or morepermanent magnets (e.g., rare earth magnets), electromagnetic coils, orother magnetized materials or structures. In yet other embodiments, thelocation marker can comprise ultrasonic emitters, electromagnetic fieldemitters, visible/infrared photon emitters, ionizing radiation emitters,etc.

In one embodiment, the location marker can be tracked using theteachings of one or more of the following U.S. Pat. Nos. 5,775,322;5,879,297; 6,129,668; 6,216,028; and 6,263,230. The contents of theafore-mentioned U.S. patents are incorporated herein by reference intheir entireties.

As mentioned, the location marker 40, when associated with the catheter10 as described above, enables the distal end 50 of the catheter to betracked during its advancement through the vasculature. The direction inwhich the catheter tip is pointing can also be ascertained, thus furtherassisting accurate catheter placement. The location marker 40 furtherassists the clinician in determining when a malposition of the catheterdistal end 50 has occurred, such as in the case where the distal end hasdeviated from a desired venous path into another vein.

With reference to FIG. 2A, in some embodiments, the location marker 40is included on a stylet 60. The stylet 60 can be preloaded into a lumenof the catheter 10 prior to advancing the catheter 10 through thevasculature 20 of the patient 25, and may extend substantially to thedistal end 50 of the catheter 10 such that the location marker 40 issubstantially co-terminal with the catheter distal end. In someembodiments, only a distal portion of the stylet 60 includes thelocation marker 40. For example, a discrete section of a distal portionof the stylet may include permanent magnetic materials. In otherembodiments, a larger portion of the stylet can comprise permanentmagnetic materials. In some embodiments, the stylet 60 is removed fromthe lumen of the catheter 10 once the distal end 50 of the catheter hasbeen positioned at the destination 30.

In greater detail, the stylet 60 includes a proximal end 62 and a distalend 70. A handle 64 is included at the stylet proximal end 62, with acore wire 66 extending distally therefrom. A magnetic assembly ofmagnetic elements that form the location marker 40 in the presentembodiment is disposed distally of the core wire 66. The magneticassembly includes the one or more magnetic materials disposed adjacentone another proximate the stylet distal end 70 and encapsulated bytubing 68. In the present embodiment, a plurality of permanent magneticelements is included, each element including a solid, cylindricallyshaped ferromagnetic stacked end-to-end with the other magneticelements. An adhesive tip 69 can fill the distal tip of the tubing 68adjacent the magnetic elements of the location marker 40. Thisconfiguration is exemplary; other location marker configurations arealso contemplated.

Note that in other embodiments, the magnetic elements described abovemay vary from the design in not only shape, but also composition,number, size, magnetic type, and position in the stylet, guidewire, etc.For example, in one embodiment, the plurality of ferromagnetic magneticelements is replaced with an electromagnetic assembly, such as anelectromagnetic coil, which produces an electromagnetic field fordetection by the sensor. Another example of an assembly usable here canbe found in U.S. Pat. No. 5,099,845 entitled “Medical InstrumentLocation Means,” which is incorporated herein by reference in itsentirety. Yet other examples of stylets including magnetic elements thatcan be employed with the catheter tip location modality described hereincan be found in U.S. application Ser. No. 11/466,602 filed Aug. 23,2006, and entitled “Stylet Apparatuses And Methods Of Manufacture,”published as U.S. Publication No. 2007-0049846 which is incorporatedherein by reference in its entirety. These and other variations aretherefore contemplated by embodiments of the present invention. Itshould be appreciated herein that “stylet” as used herein can includeany one of a variety of devices configured for removable placementwithin a lumen of the catheter to assist in placing a distal end of thecatheter in a desired location within the patient's vasculature.

With reference to FIG. 2B, in another embodiment, the location marker 40including a plurality of magnetic elements or other suitable structureis included on a distal portion of the guidewire 80 proximate a distalend 90 thereof. In this embodiment, the distal tip 90 of the guidewire80 is advanced to the destination 30 within the patient 25. The catheter10 can then be advanced over the guidewire 80 until the distal end 50 ofthe catheter 10 is at the destination 30. The guidewire 80 can then beremoved from the patient 25.

FIG. 2C gives various details regarding a distal portion of a stylet 92including the location marker 40 configured in accordance with onepossible embodiment. A coil assembly 96 is included proximate a styletdistal end 94 and is operably connected to leads 96A. The leads 96A arein turn operably connected to corresponding circuitry in a tip locationsystem (FIG. 10) configured to produce an electric pulse signal so as toenable the coil assembly 96 to be electrically pulsed during operationand produce an electromagnetic field having a predetermined frequency orpattern that is detectable by one or more sensors included in a detectorplaced proximate to the patient 25 (FIG. 3) during transit of thecatheter through the vasculature when the coil assembly is within thedetectable range of the sensor. Note that the coil assembly describedherein is but one example of a field-producing element, or a componentcapable of producing an electromagnetic field for detection by thesensor. Indeed, other devices and assembly designs can be utilized hereto produce the same or similar functionality.

The coil assembly 96 and leads 96A are disposed within tubing 98 thatextends the length of the stylet 92. The coil assembly and leads can beprotected in other ways as well. A core wire 99 can be included withinthe tubing 98 in one embodiment to offer stiffness and/or directionaltorqueability to the stylet 92. The core wire 99 in one embodimentincludes nitinol and can extend to the distal end 94 of the stylet 92 orterminate proximal thereto.

With reference to FIG. 3, in certain embodiments, a tip locationdetector 100 is positioned adjacent or proximate to the patient 25 asthe catheter 10 is advanced to the destination 30 within the patientvasculature. For example, in the illustrated embodiment, the detector100 can be positioned on the chest of the patient 25.

The detector 100 includes in the present embodiment one or more sensors110. Two sensors 110 are shown schematically in the illustratedembodiment. In some embodiments, the location detector 100 can includeone or more, two or more, etc. sensors 110. For instance, in oneembodiment, the detector 100 includes ten sensors 110 placed in aspaced-apart configuration within the detector body. The sensors 110 areconfigured to detect the location marker 40. For example, each sensor110 can be configured to detect the strength of a magnetic fieldproduced by the location marker 40 at the position of the sensor 110 andby so doing enable the system to calculate an approximate location andorientation of the location marker.

In some embodiments, the detector 100 defines one or more branches 120.In some embodiments, two branches 120 a, 120 b of the detector 100extend upward and outward from a lower branch 120 c such that thedetector 100 is substantially “Y”-shaped. Terms such as “upper” and“lower” are used herein by way of convenience, and not limitation, todescribe the embodiments depicted in the figures. Accordingly, the upperbranches 120 a, 120 b are closer to the head of the patient 25 than isthe lower branch 120 c.

FIG. 3 illustrates an axis convention that will be used throughout theremainder of this disclosure by way of convenience and not limitation.In the illustrated embodiment, three dimensional Cartesian coordinatesystem is centered on the lower branch 120 c of the detector 100. Thepositive portion of the X-axis runs toward the right of the page (i.e.,toward the left side of the patient 25), the positive portion of theY-axis runs toward the top of the page (i.e., toward the head of thepatient 25), and the positive portion of the Z-axis extends directly outof the page (i.e., away from the chest of the patient 25). Accordingly,the portion of the Z-axis extends through the patient 25 such that amore negative Z-value is deeper within the patient relative to thedetector 100.

In some embodiments, a portion of the detector 100 can be expected to bemore sensitive to the initial detection of the location marker 40 thanother portions of the detector 100. For example, in some embodiments,the location marker 40 may be expected to pass beneath (i.e., below,relative to the Z-axis) the branch 120 a of the detector 100 beforepassing beneath other portions of the detector 100 as the catheter 10 isadvanced toward the superior vena cava of the patient 25. In someembodiments, data processing algorithms based on such an expectation canbe used to reduce or eliminate misidentification of a position of thelocation marker 40 or “false positive” identifications that representsomething other than the marker 40.

With reference to FIG. 4, in some embodiments, the detector 100 is incommunication with a processor 130. The processor 130 can comprise anysuitable storage and/or computing device, such as, for example, acomputer configured to run one or more programs, or a microprocessor.The processor 130 can be configured to receive data obtained by thedetector 100 (e.g., via the sensors 110) and to process the data todetermine a position of the location marker 40, as further describedbelow. In some embodiments, the processor 130 utilizes detection zonesin processing the data received from the detector 100 and/or indelivering a representation of the position of the location marker 40for display. One possible environment in which the processor 130 isincluded is seen in FIG. 10, as described further below.

In some embodiments, the processor 130 utilizes a first detection zone140 and a second detection zone 150. In some embodiments, the firstdetection zone 140 encompasses a relatively large portion of the upperbranches 120 a, 120 b of the detector 100. For example, in someembodiments, the first detection zone 140 extends from a base portion ofeach branch 120 a, 120 b to a position above the detector 100 in thepositive Y direction, beyond the detector 100 in both the positive andnegative X directions, and below the detector 100 in the negative Zdirection. As such, the first detection zone 140 and second detectionzone 150 define imaginary rectangular volumes of space proximate thedetector 100 that extend into the body of the patient 25. In oneembodiment, for example, the size of the first detection zone 140 isabout 28 centimeters (cm) in the X direction, about 10.5 cm in the Ydirection, and about 8 cm in the Z direction. The size of the seconddetection zone 150 is about 23 cm in the X direction, about 15 cm in theY direction, and about 11 cm in the Z direction. Other detection zonedimensions are also possible.

In other embodiments, the first detection zone 140 does not include thedetector 100. For example, in some embodiments, the first detection zone140 can be substantially as shown in FIG. 4, but begins at a positionbelow the detector 100 (i.e., at a position in the negative Zdirection), and extends toward more negative Z-values.

One or more of the first and second detection zones 140, 150 can includea portion of the path 35 along which the catheter 10 is advanced. Insome embodiments, the first detection zone 140 includes a portion of thepath 35 that is proximal of a portion of the path 35 that runs throughthe second detection zone 150. In other embodiments, only the firstdetection zone 140 may include a portion of the path 35.

In some embodiments, the first and second detection zones 140, 150 canoverlap each other. For example, in the illustrated embodiment, thesecond detection zone 150 includes a portion of the upper branches 120a, 120 b that is also included in the first detection zone 140. Thefirst and second detection zones 140, 150 can define the same ordifferent areas in any of the XY-, YZ-, or ZX-planes and can define thesame or different volumes.

More or fewer detection zones are possible. Additionally, detectionzones can define a variety of shapes, such as, for example, boxes,spheres, ellipsoids, and paraboloids. Detection zones may be suitablydescribed in a variety of coordinate systems, such as, for example,Cartesian or polar coordinates.

FIG. 5 illustrates another embodiment of a detector 100 having an upperdetection zone 160 and a lower detection zone 170 superimposed thereon.FIG. 5 provides approximate dimensions and approximate relativepositions of the upper and lower detection zones 160, 170. In theillustrated embodiment, the detection zones 160, 170 begin at a positionof about −1 centimeter from the origin of the Z-axis and terminate at aposition of about −6 cm from the origin of the Z-axis.

Other dimensions than those illustrated in the instant embodiment arealso possible. For example, one or more of the upper and lower detectionzones 160, 170 can extend from about −1 centimeter to about −25centimeters, from about −1 centimeter to about =15 centimeters, fromabout −1 centimeter to about −12 centimeters, or from about −1centimeter to about −9 centimeters from the Z-origin. In someembodiments, the upper limit of the depth of one or more of the upperand lower detection zones 160, 170 can be within a range of betweenabout 0 centimeters and −5 centimeters, and the lower limit of the depthof one or more of the first and second detection zones 160, 170 can bewithin a range of between about −5 centimeters and about −30centimeters. Other ranges for the upper and lower detection zones 160,170 are possible. The first and second detection zones 140, 150 can bedefined in one embodiment by the same or different dimensions as theupper and lower detection zones 160, 170.

FIG. 6 depicts a catheter 10 having the location marker 40 positionedbeneath the detector 100 of FIG. 4. A magnetic field produced by thelocation marker 40 is schematically illustrated by concentric circles.In the illustrated embodiment, the location marker 40 is within thefirst detection zone 140.

With reference to FIG. 7, in certain embodiments, the processor 130 canbe in communication with a display device 200, such as, for example agraphical user interface on a screen (see also FIG. 10). In someembodiments, the display 200 includes a detector representation 210,which can depict a projection of the detector 100 in the XY-plane. Adepth indicator 220 can depict a Z-coordinate of the location marker 40.

As shown in FIG. 8, in some embodiments, the display 200 can include amarker symbol 230 that represents a position of the location marker 40relative to the detector 100 (compare FIG. 6), such as within a portionof the vasculature of the patient when the detector is positioned on thepatient's chest. The marker symbol 230 can also indicate a direction inwhich the location marker 40 is moving or the direction that thelocation marker 40 is facing. For instance, in the view shown in FIG. 8,the location marker 40 indicates that the catheter 10 is generallyadvancing from the left side of the page toward the right side thereof.As further discussed below, in some embodiments, whether or not themarker symbol 230 is displayed and/or the position on the display 200 atwhich the marker symbol 230 is displayed is based on informationreceived from the processor 130.

In some embodiments, the display 200 can include button icons 240 thatcorrespond to buttons or controls located on a button control interfaceincluded in a console (FIG. 10) in which the display 200 is housed.Further informational or control icons 250 can be included on thedisplay 200. In further embodiments, the display 200 comprises a touchscreen such that a user can deliver instructions to the processor 130and/or the tip location detector 100 via the buttons or controlsappearing on the screen. Other systems and methods for providinginstructions to the processor 130 and/or the tip location detector 100are also possible.

With reference to FIG. 9, in certain embodiments, a tip location system300 can include the detector 100, the processor 130, and/or the display200. The system 300 can be configured to detect the location marker 40and to display the marker symbol 230, as described above. In someembodiments, the detector 100 is positioned relative to the patient 25.The system 300 is then zeroed to calibrate to (or account for) localmagnetic fields. In some embodiments, after the system 300 has beenzeroed, the system 300 actively measures magnetic fields. For example,in an implementation where the location marker 40 includes a pluralityof magnetic elements positioned at the distal end 70 of a stylet 60pre-loaded in the catheter 10 (see the stylet 60 shown in FIG. 2A), thedetector 100 can monitor or measure magnetic fields via the sensors 110during transit of the catheter through the vasculature of the patient.The measurements can be obtained continuously, for example, oriteratively at regular or irregular intervals as determined by theprocessor 130 or other suitable control component of the system 300.

In some embodiments, a model 310 of the location marker 40 is stored inthe system 300. For example, in some embodiments, the model 310 isstored in a memory portion of the processor 130 for access when needed.The model 310 can comprise magnetic strength patterns that are eachrepresentative of a magnetic field produced by the location marker 40 atone of a multitude of possible marker locations. In some embodiments,the processor 300 compares data received from the detector 100, whichdata relate to the position of the location marker 40 with respect toone or more of the detector sensors 110, with the model 310 toultimately determine whether the location marker 40 is within one ormore of the detection zones 140, 150.

In some embodiments, the processor 130 can execute a program or set ofexecutable instructions that implements one or more algorithms fordetermining how well a data set of a possible location marker positiongathered by the detector 100 corresponds with the model 310. The programcan provide a confidence level regarding the data set. In someembodiments, the confidence level indicates how well such a data set andthe model 310 match. In further embodiments, the confidence levelindicates the degree of certainty that the location marker 40 is at aspecific position. In still further embodiments, the confidence levelrepresents how well a gathered data set and the model 310 match as wellas the degree of certainty that the location marker 40 is at a specificposition. The confidence level can be expressed as an absolute or ascalar value, in some embodiments. An example of a program that issuitable for use with certain embodiments described herein is softwaremarketed under the trademark ZAP™, which is distributed by LucentMedical Systems.

In certain embodiments, the processor 130 provides instructions todepict the marker symbol 230 (FIG. 8) corresponding to the detectedposition of the location marker 40 on the display 200 when certainconditions are met. For example, in some embodiments, after the system300 has been zeroed or calibrated, in order for the display to initiallydepict the marker symbol 230, the center of the location marker 40 mustbe identified as being within the first detection zone 140 with aconfidence level above a first threshold value (or with a confidencelevel within a first range). For example, in certain embodiments thatuse ZAP™ software, the center of the location marker 40 must beidentified as being within the first detection zone 140 (which can, forexample, be at a depth of between about 1 centimeter and about 8centimeters below the detector 100), with a COST of less than or equalto 500. COST is a term associated with ZAP™ software that represents inone embodiment an absolute value of a comparative match between measuredmagnetic field data as detected by the detector 100 and predictedmagnetic field data as computed by the processor 130. The COST value ison a reverse scale such that a lower value represents a relativelyhigher threshold value or level of confidence.

In some embodiments, multiple identification and validation sequences,or solution sequences, regarding a position of a possible locationmarker 40 are performed before the marker symbol 230 is initiallydisplayed. For example, in some embodiments, the conditions relating toresolution of the possible location marker position with respect to thefirst and/or second detection zones 140, 150 and determination of aconfidence level described in the preceding paragraph must be satisfiedin eight consecutive sequences before the marker symbol 230 willinitially be displayed. In other embodiments, the conditions must be metin five consecutive sequences before an initial display of the markersymbol 230. In certain of such embodiments, subsequent cycles may aid inpinpointing or converging on a more accurate location of the markersymbol 230, such that the marker symbol 230 may drift slightly after itis initially displayed. Other series of solution sequences are alsopossible.

After the initial display of the marker symbol 230, separate conditionsmay be implemented in order to continue displaying the maker symbol 230after it has met the conditions to be displayed initially. For examplein some embodiments, the marker symbol 230 will continue to be displayedif the center of the location marker 40 is within either the firstdetection zone 140 or the second detection zone 150 and if theconfidence level is above a second threshold value (or within a secondconfidence range). In some embodiments, the second threshold value islower then the first threshold value (i.e., the second threshold valuecan represent a lesser degree of confidence than does the firstthreshold value). For example, in certain embodiments that use ZAP™software, the center of the location marker 40 must be identified asbeing within the first or second detection zones 140, 150 with a COST ofless than or equal to 1000 in order for the marker symbol 230 tocontinue to be displayed.

In further embodiments, the first and second detection zones 140, 150can be expanded in size after the initial identification of the locationmarker 40 and initial display of the marker symbol 230. For example, insome embodiments, the first and second detection zones 140, 150 extendbetween a depth of about 1 centimeter and about 8 centimeters below thedetector 100 before the initial display of the marker symbol 230, andcan extend between a depth of about 1 centimeter and about 12centimeters below the detector after the initial display of the markersymbol 230. Of course, modification of the detection zone sizes inamounts different from those outlined above is also possible.

An initial display of the marker symbol 230 can occur after events otherthan or in addition to zeroing the system 300. For example, in someembodiments, the system 300 may be turned off after having displayed themarker symbol 230. Upon being turned on again, a subsequent showing ofthe marker symbol 230 can be referred to as an initial display of themarker symbol 230. In other embodiments, the system 300 can be resetwithout powering down such that a first display of the marker symbol 230after the resetting event would be an initial display of the markersymbol 230.

In some embodiments, the system 300 can employ separate criteria fordisplaying the marker symbol 230 after the system 300 has tracked theposition of the location marker 40, e.g., after initially displaying andcontinuing to display the marker symbol 230. For example, in someembodiments, if the location marker 40 is moved out of the sensing rangeof the detector 100, e.g., outside of the first and second detectionzones 140, 150 and subsequently moved back into the sensing range, thetracking can start again if the detector 100 senses that the locationmarker 40 is within the first detection zone 140 or the second detectionzone 150 and is above the first threshold value, e.g., COST is less thanor equal to 500. Similarly, in some embodiments, if the system 300 losesthe tracking of the location marker 40, e.g., fails to identify theposition of the location marker 40 during a solution sequence, thetracking can commence again if the detector 100 senses that the locationmarker 40 is within the first detection zone 140 or the second detectionzone 150 and is above the first threshold value.

In some embodiments, the system 300 may be preset such that thethreshold values are fixed. In other embodiments, the system 300 can bealtered by a user to vary one or more threshold values, as desired.

FIG. 10 depicts in simplified form an example implementation of a tiplocation system, i.e., the system 300 partially depicted in FIG. 9, inwhich embodiments of the present invention can be practiced. As shown,the system 300 generally includes a console 420, display 200, probe 440,and detector 100, each of which is described in further detail below. Asmentioned above, the system 300 is employed to ultimately position adistal end 50 of the catheter 10 in a desired position within thepatient vasculature. In one embodiment, the desired position for thecatheter distal end 50 is proximate the patient's heart, such as in thelower one-third (⅓^(rd)) portion of the SVC (FIG. 1). Of course, thesystem 300 can be employed to place the catheter distal end in otherlocations.

A processor 422, including non-volatile memory such as EEPROM forinstance, is included in the console 420 for controlling system functionduring operation of the system 300, thus acting as a control processor.A digital controller/analog interface 424 is also included with theconsole 420 and is in communication with both the processor 422 andother system components to govern interfacing between the probe 440,detector 100, and other system components.

The system 300 further includes ports 452 for connection with thedetector 100 and optional components 454 including a printer, storagemedia, keyboard, etc. The ports in one embodiment are USB ports, thoughother port types or a combination of port types can be used for this andthe other interfaces connections described herein. A power connection456 is included with the console 420 to enable operable connection to anexternal power supply 458. An internal battery 460 can also be employed,either with or exclusive of an external power supply. Power managementcircuitry 459 is included with the digital controller/analog interface424 of the console to regulate power use and distribution.

The display 200 in the present embodiment is an LCD-based device, isintegrated into the console 420, and is used to display information tothe clinician during the catheter placement procedure. In anotherembodiment, the display may be separate from the console. In oneembodiment, the console button interface 432 (FIGS. 1, 8C) and buttonsincluded on the probe 440 can be used to control the display 200 andthus assist the clinician during the placement procedure.

In one embodiment the system 300 optionally includes the probe 40, whichis employed in connection with ultrasound (“US”)-based visualization ofa vessel, such as a vein, in preparation for insertion of the catheter10 into the vasculature. Such visualization gives real time ultrasoundguidance for initially introducing the catheter into the vasculature ofthe patient and assists in reducing complications typically associatedwith such introduction, including inadvertent arterial puncture,hematoma, pneumothorax, etc. After the catheter has been initiallyplaced in the patient vasculature, the system 300 can be used to locatethe distal end 50 of the catheter 10 via detection of a correspondinglocation marker, as has been described above. In one embodiment, anothermodality can be added to the system 300, wherein an ECG-basedconfirmation of correct catheter distal tip placement with respect to anode of the patient's heart is employed. Further details regarding theUS, tip location, and ECG-based modalities of the system 300 can befound in U.S. application Ser. No. 12/323,273, filed Nov. 25, 2008, andentitled “INTEGRATED SYSTEM FOR INTRAVASCULAR PLACEMENT OF A CATHETER,”published as U.S. Publication No. 2009-0156926 which is incorporatedherein by reference in its entirety.

FIG. 10 shows that the probe 440 further includes button and memorycontroller 442 for governing button and probe operation. The button andmemory controller 442 can include non-volatile memory, such as EEPROM,in one embodiment. The button and memory controller 442 is in operablecommunication with a probe interface 444 of the console 420, whichincludes a piezo input/output component 444A for interfacing with apiezoelectric array included in the probe, and a button and memoryinput/output component 444B for interfacing with the button and memorycontroller 442.

Embodiments of the present invention may comprise a special purpose orgeneral-purpose computer including computer hardware. Embodiments withinthe scope of the present invention also include computer-readable mediafor carrying or having computer-executable instructions or datastructures stored thereon. Such computer-readable media can be anyavailable media that can be accessed by a general purpose or specialpurpose computer. By way of example, and not limitation,computer-readable media can include physical (or recordable-type)computer-readable storage media, such as, RAM, ROM, EEPROM, CD-ROM orother optical disk storage, magnetic disk storage or other magneticstorage devices, non-volatile and flash memory, or any other mediumwhich can be used to store desired program code means in the form ofcomputer-executable instructions or data structures and which can beaccessed by a general purpose or special purpose computer.

In this description and in the following claims, a “network” is definedas one or more data links that enable the transport of electronic databetween computer systems and/or modules. When information is transferredor provided over a network or another communications connection (eitherhardwired, wireless, or a combination of hardwired or wireless) to acomputer, the computer properly views the connection as acomputer-readable medium. Thus, by way of example, and not limitation,computer-readable media can also include a network or data links whichcan be used to carry or store desired program code means in the form ofcomputer-executable instructions or data structures and which can beaccessed by a general purpose or special purpose computer.

Computer-executable instructions comprise, for example, instructions anddata which cause a general purpose computer, special purpose computer,or special purpose processing device to perform a certain function orgroup of functions. The computer executable instructions may be, forexample, binaries, intermediate format instructions such as assemblylanguage, or even source code. Although the subject matter has beendescribed in language specific to structural features and/ormethodological acts, it is to be understood that the subject matterdefined in the appended claims is not necessarily limited to thedescribed features or acts described above. Rather, the describedfeatures and acts are disclosed as example forms of implementing theclaims.

Those skilled in the art will appreciate that the embodiments of thepresent invention may be practiced in computing environments with one ormore types of computer system configurations, including, personalcomputers, desktop computers, laptop computers, message processors,hand-held devices, multi-processor systems, microprocessor-based orprogrammable consumer electronics, network PCs, minicomputers, mainframecomputers, mobile telephones, PDAs, pagers, and the like. Embodimentsmay also be practiced in distributed system environments where local andremote computer systems, which are linked (either by hardwired datalinks, wireless data links, or by a combination of hardwired andwireless data links) through a network, both perform tasks. In adistributed system environment, program modules may be located in bothlocal and remote memory storage devices.

Thus, in one embodiment, and as depicted in FIG. 11, a method 500 fordisplaying a position of a medical device includes calibrating thesystem 300 at stage 510. At stage 520, a first set of detected positiondata relating to a possible first position of a location marker isobtained. As has been described, the position data can relate to anX-Y-Z-coordinate on a Cartesian coordinate axis grid centered on orproximate to the detector 100, as shown in FIG. 4. In the presentembodiment, the position data includes data from the magnetic fieldproduced by the magnetic assembly of the location marker of the styletas sensed by each of the sensors 110 of the detector 100. These data areforwarded to the processor 130 of the system 300.

At stage 525, the possible first position of the location marker isdetermined. In one embodiment, the possible first position relates tothe initial detection of the location marker by the system and isestimated by a neural net functionality provided by the processor 130 orother suitable component of the system. In brief, the neural netfunctionality continually monitors detected position data and provides abest guess of the position of the location marker. In the presentembodiment, the neural net functionality is pre-programmed, or“trained,” with sample location marker position data, i.e., magneticfield data, for a variety of possible location marker positions andorientations with respect to the detector 100. This training enables theneural net to make a best fit determination between its pre-programmedsample position data and the detected position data obtained in stage520 to determine a possible first position of the location marker.Determination of the possible first position of the location marker inthis stage is made in the present embodiment by the processor 130 orother suitable component via execution of the ZAP™ Software.

At stage 530, a first confidence level relating to a match between thefirst set of detected position data and a first set of predictedposition data relating to the possible first position of the locationmarker is assigned. The predicted position data in the presentembodiment is provided by the processor 130 or other suitable componentvia execution of the ZAP™ Software, which calculates the predicted databased on physics-based characteristics of the location marker (in thepresent embodiment, a stack of magnetic elements as seen in FIG. 2A)assumed to be positioned at the possible first position. The resultingfirst set of predicted position data includes data for each sensor ofthe detector on the chest of the patient and is compared to thecorresponding first set of detected position data for each sensor. Thiscomparison yields the first confidence level, which is a quantitative,absolute value indicating the degree of matching between the detecteddata obtained at stage 520 and the predicted data. As has been discussedabove, the COST value produced by the ZAP™ Software is one example of aconfidence level that can be employed in the present method 500. Again,further details regarding the ZAP™ Software and the COST value are givenin one or more of U.S. Pat. Nos. 5,775,322, 5,879,297, 6,129,668,6,216,028, and 6,263,230, each of which is incorporated herein byreference in its entirety. Of course, other algorithms utilizing otherconfidence level configurations can also be used.

In one embodiment, stages 525 and 530 above are iteratively executed inorder to better pinpoint the possible first position of the locationmarker. With each iteration, the possible first position is modified,which in turn modifies the set of predicted position data, in theinterest of better matching the predicted data with the detectedposition data obtained at stage 520. This in turn increases the firstconfidence level, i.e., reduces the COST value in the present embodimentwhere the ZAP™ Software is employed. Such an iterative method is alsoreferred to as a convergence algorithm. Once a minimum COST value isobtained via the convergence algorithm, the method can proceed. In otherembodiments, a predefined number of iterations can be performed; instill other embodiments no additional iterations are performed.

At stage 540, it is determined whether the first confidence level meetsor exceeds a first threshold, such as a predetermined COST value in thepresent embodiment, as described further above. As described above, thepresent stage, as well as stages 525 and 530, is executed in the presentembodiment by the ZAP™ Software, or other suitable algorithm. If thefirst confidence level fails to meet or exceed the first threshold, suchas a COST value of 500 in one embodiment, the possible location markeris not displayed and the method cycles back to stage 520 to continuemonitoring for the presence of a possible location marker.

If the first confidence level meets or exceeds the first threshold,however, stage 550 is executed, wherein it is determined whether thefirst position of the possible location marker is within a firstdetection zone, such as the first detection zone 140 shown in FIG. 4.This stage is executed in one embodiment by the processor 130 of thesystem 300, as shown in FIG. 10. If the first position is not within thefirst detection zone, the possible location marker is not displayed andthe method cycles back to stage 520 to continue monitoring for thepresence of a possible location marker. If the first position is withinthe first detection zone, however, stage 560 is executed, wherein thefirst position of the location marker is displayed, such as on thedisplay 200 shown in FIGS. 8 and 10, for instance.

In one embodiment, stages 520 through 550 are repeated in sequence apredetermined number of times before stage 560 is executed and thelocation marker is displayed. In one embodiment, stages 520 through 550are successfully executed eight times, after which the location markeris displayed. Of course, the number of iterations can vary.

Reference is now made to FIG. 12. In one embodiment, the method fordisplaying the position of a medical device can continue after displayof the first position of the location marker at stage 560 such thatfurther advancement of the location marker 40 associated with themedical device, such as the catheter 10 progressing through avasculature, can be progressively displayed. At stage 570, a second setof detected position data relating to a possible second position of thelocation marker is obtained.

At stage 575, the possible second position of the location marker isdetermined. In the present embodiment, the possible second positionrelates to the first position of the location marker, and as such nobest fit guessing by a neural net component of the ZAP™ Software orother suitable algorithm need be performed.

At stage 580, a second confidence level relating to a match between thesecond set of detected position data and a second set of predictedposition data, is assigned. As was the case with stages 525 and 530 ofFIG. 11, stages 575 and 580 can be iteratively performed in the presentembodiment in order to find a minimum COST value. In other embodiments,a predetermined number of iterations, or no iterations, can beperformed.

At stage 590, it is determined whether the second confidence level meetsor exceeds a second threshold, such as a predetermined COST value in thepresent embodiment, as described further above. As has been described,the second threshold in one embodiment is relatively lower, i.e., theCOST value is higher, than the first threshold. In the presentembodiment, the COST value is 1000, for instance. If the secondconfidence level fails to meet or exceed the second threshold, thepossible location marker is not displayed and the method can cycle backto stage 570 to continue monitoring for further location marker positiondata.

If the second confidence level meets or exceeds the second threshold,however, stage 600 is executed, wherein it is determined whether thesecond position of the location marker is within at least one of thefirst and second detection zones, such as the first detection zone 140and second detection zone 150 shown in FIG. 4. If not, the possiblelocation marker is not displayed and the method can cycle back to stage570 to continue monitoring for further location marker position data. Ifthe second position is within the first detection zone and/or the seconddetection zone, however, stage 610 is executed, wherein the secondposition of the location marker is displayed.

In one embodiment, stages 570 through 600 are repeated in sequence apredetermined number of times before stage 610 is executed and thelocation marker is displayed. In another embodiment, no repetitions ofthe sequence are performed before display at stage 610 is executed.

In one embodiment, stage 580 includes ensuring that the second positionof the location marker is within a predetermined distance range from thefirst position of the location marker within a predetermined amount oftime so as to prevent maverick detection of non-location marker targetsfrom being validated as location markers. It is noted that one or moreof stages 570-610 of the method 500 can be successively repeated to findand display additional positions of the location marker duringadvancement of the catheter 10 through the patient's vasculature.

Embodiments of the invention may be embodied in other specific formswithout departing from the spirit of the present disclosure. Thedescribed embodiments are to be considered in all respects only asillustrative, not restrictive. The scope of the embodiments is,therefore, indicated by the appended claims rather than by the foregoingdescription. All changes that come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

What is claimed is:
 1. A method of depicting a position of a catheter that is within a patient, the method comprising: moving a location marker associated with the catheter along a path in a direction from an entry point toward a destination, wherein the location marker produces a magnetic field; positioning a detector having a first detection zone and a second detection zone such that at least the first detection zone includes a portion of the path, wherein the portion of the path included in the first detection zone is proximal relative to any portion of the path included in the second detection zone; obtaining, via the detector, first measurements of the magnetic field produced by the location marker; determining a first confidence level regarding a first position of the location marker based on the first measurements; displaying an initial representative image of the location marker if the first position is within the first detection zone and the confidence level is above a first threshold value; obtaining, via the detector, second measurements of the magnetic field produced by the location marker; determining a second confidence level regarding a second position of the location marker based on the second measurements; and displaying a subsequent representative image of the location marker if the second position is within one or more of the first and second detection zones and the confidence level is above a second threshold value different than the first threshold value.
 2. The method of claim 1, wherein the second threshold value is lower than the first threshold value.
 3. The method of claim 1, further comprising withholding the initial representative image of the location marker from being displayed if the first position is within the second detection zone and the first confidence level is above the first threshold value.
 4. The method of claim 1, further comprising: tracking movement of the location marker after having displayed the initial representative image of the location marker; and discontinuing to track movement of the location marker prior to displaying the subsequent representative image.
 5. The method of claim 4, wherein the second threshold value is lower than the first threshold value.
 6. A system for depicting a position of a catheter, the system comprising: a detector configured to obtain first and second measurements of a magnetic field produced by a location marker associated with the catheter, wherein a first detection zone and a second detection zone are defined relative to the detector; a processor in communication with the detector, wherein the processor is configured to: receive the first measurements from the detector; compare the first measurements with a model of the location marker; provide a first confidence level regarding a first position of the location marker; receive the second measurements from the detector; compare the second measurements with the model of the location marker; and provide a second confidence level regarding a second position of the location marker; and a display device configured to show an image representative of the location marker, wherein the system is configured to show an initial display of the image only if the first confidence level is above a first threshold value and the first position is within the first detection zone, and wherein the system is configured to show a subsequent display of the image if the second confidence level is above a second threshold value different from the first threshold value and the second position is within one or more of the first and second detection zones.
 7. The system of claim 6, wherein the location marker is temporarily or permanently associated with the catheter and includes at least one of the following: a magnetic component; and an electromagnetic field-producing component.
 8. The system of claim 6, wherein the location marker is a magnetic component included on a stylet that is removably inserted into a lumen of the catheter.
 9. A method for displaying a position of a medical device during placement of the medical device into a patient using a system including a processor, the method comprising: (a) obtaining a first set of detected position data relating to a location marker associated with the medical device; (b) determining a possible first position of the location marker; (c) assigning a first confidence level relating to a match between the first set of detected position data and a first set of predicted position data relating to the possible first position; (d) determining that the first confidence level meets or exceeds a first threshold; (e) determining that the first position of the location marker is within a first detection zone if the first confidence level meets or exceeds the first threshold; (f) displaying the first position of the location marker if the first position of the location marker is within the first detection zone; (g) obtaining a second set of detected position data relating to the location marker; (h) determining a possible second position of the location marker; (i) assigning a second confidence level relating to a match between the second set of detected position data and a second set of predicted position data relating to the possible second position; (j) determining that the second confidence level meets or exceeds a second threshold different from the first threshold; (k) determining that the second position of the location marker is within at least one of the first detection zone and a second detection zone if the second confidence level meets or exceeds the second threshold; and (l) displaying the second position of the location marker if the second position of the location marker is within at least one of the first detection zone and the second detection zone.
 10. The method of claim 9, wherein stage (b) further comprises: (b) determining a possible first position of the location marker via a neural net best fit algorithm; and wherein stage (k) further comprises: (k) determining that the second position of the location marker is within at least one of the first detection zone and a second detection zone, the first detection zone at stage (i) including dimensions larger than when the first set of detected position data was obtained at stage (a).
 11. The method of claim 9, further comprising calibrating the system before executing stage (a).
 12. The method of claim 9, wherein stage (k) further comprises: (k) ensuring that the second position of the location marker is within a predetermined distance range from the first position of the location marker within a predetermined amount of time.
 13. The method of claim 9, wherein the location marker includes a magnetic component attached to the medical device, wherein the first position and the second position of the location marker are defined with respect to an X, Y, Z coordinate axis grid including an origin at or proximate to the detector, and wherein a depth of the first detection zone is at least 8 cm.
 14. The method of claim 9, wherein at least stages (b) and (c) are repeatedly executed in succession a predetermined number of times before stage (d) is executed.
 15. The method of claim 9, wherein a shape of at least one of the first and second detection zones is selected from the list consisting of: square box, rectangular box, triangular volume, spherical, ellipsoid; and paraboloid.
 16. A computer program product for implementing a method for displaying a position of a medical device during placement of the medical device into a patient, the computer program product including one or more non-transitory computer-readable media having stored thereon computer executable instructions that, when executed by a processor, cause a computer system to perform the following: (a) obtain a first set of detected position data relating to a location marker associated with the medical device; (b) determine a possible first position of the location marker; (c) assign a first confidence level relating to a match between the first set of detected position data and a first set of predicted position data relating to the possible first position; (d) determine that the first confidence level meets or exceeds a first threshold; (e) determine that the first position of the location marker is within a first detection zone if the first confidence level meets or exceeds the first threshold; (f) display the first position of the location marker if the first position of the location marker is within the first detection zone; (g) obtain a second set of detected position data relating to the location marker; (h) determine a possible second position of the location marker; (i) assign a second confidence level relating to a match between the second set of detected position data and a second set of predicted position data relating to the possible second position; (j) determine that the second confidence level meets or exceeds a second threshold different from the first threshold; (k) determine that the second position of the location marker is within at least one of the first detection zone and a second detection zone if the second confidence level meets or exceeds the second threshold; and (l) display the second position of the location marker if the second position of the location marker is within at least one of the first detection zone and the second detection zone. 